When plastic and glass materials are exposed to an environment having a significantly different temperature and humidity, fog phenomena in which moisture is condensed on the surface of the materials in the form of fine water drops occur to rapidly reduce the transparency of the surface. For this reason, persons in spectacles suffer much inconvenience, particularly in the winter or summer season where the difference between indoor and outdoor temperatures is great. Also, in various fields, including bathroom mirrors, automobile glass and greenhouse glass, methods for imparting hydrophilicity to surfaces to prevent fog phenomena have been developed.
Currently commercialized liquid anti-fog agents are based on a liquid anionic surfactant, which, when applied to lens surfaces, shows a water contact angle of less than 10°. However, such anti-fog agents merely form a temporary layer in a physically adsorbed state rather than forming a permanent chemical bond with lens surfaces. Thus, these anti-fog agents are easily peeled off even by weak stimulation and can provide only temporary effects.
Recently, studies on functional coatings for preventing fog phenomena by chemically bonding lens surfaces with superhydrophobic fluorine compounds or compounds having hydrophilic groups have been actively conducted, but a technology of forming superhydrophilic thin films using metal ion chelates has not yet been developed.
Meanwhile, fuel cells, which is being received as next generation energy sources due to environment-friendly characteristics, use fuel gases (hydrogen, methanol, or other organic materials) and an oxidant (oxygen or air) and produce electric powder using electrons generated during oxidation/reduction reactions between the fuel gases and the oxidant. Such fuel cells comprise a continuous complex, which consists of a membrane electrode assembly (MEA) including a hydrogen ion exchange membrane interposed between an anode and a cathode, and a bipolar plate of collecting generated electricity and supplying fuel. In the anode, hydrogen or methanol as fuel is supplied and acts on an electrode catalyst to generate hydrogen ions (H+, protons), and in the cathode, hydrogen ions passed through the hydrogen ion exchange membrane bind to oxygen to produce pure water.
Each of the anode and the cathode consists of a catalyst layer, where oxidation/reduction reactions between reactants occur, and a support layer (also referred to as a gas diffusion layer) for supporting the catalyst layer. In addition to the role of supporting the catalyst layer, the support layer serves as a gas diffusion layer for diffusing reactants toward the catalyst layer, a collector for transferring electric currents generated in the catalyst layer to the bipolar plate, and a passage for discharging produced water out of the catalyst layer, and functions to cause a suitable amount of water to be present in the hydrogen ion exchange membrane.
A polymer electrolyte membrane fuel cell (PEMFC) that uses hydrogen as fuel in low humidity conditions can operate in a wide temperature range, and thus has advantages in that a cooling device is not required and sealing parts can be simplified. Also, it uses non-humidified hydrogen as fuel and thus does not require the use of a humidifier. In addition, it can be rapidly driven. Due to such advantages, it receives attention as a power source device for cars and homes. Furthermore, it is a high-output fuel cell having a current density higher than those of other types of fuel cells, which can operate in a wide temperature range and has a simple structure and rapid starting and response characteristics.
In the cases of sulfonated polymer electrolyte membranes, including perfluorosulfonated polymer Nafion, or hydrocarbons such as sulfonated polyether ether ketone, sulfonated polyethersulfone, sulfonated polystyrene, and sulfonated polyimide, a decrease in hydrogen ion conductivity resulting from a decrease in water content in the membranes occurs. For this reason, the use of these membranes at high temperatures (more than 100° C.) requires strict water control and complex systems.
In an attempt to solve the above-described problems, studies on various kinds of organic/inorganic composite electrolyte membranes, in which proton conducting fillers showing high hydrogen ion conductivity and water absorption are added to organic polymers, have been conducted. However, these membranes are not used in practice, because the performance thereof is reduced in low humidity conditions.